Many questions -- such as the motive -- remain unanswered since the October 1 massacre in which 58 were killed and hundreds injured when the gunman, Stephen Paddock, opened fire on the Route 91 Harvest music festival from the 32nd floor of the Mandalay Bay Resort and Casino.

Clark County Sheriff Joe Lombardo said the FBI is investigating an individual of federal interest related to the case. Charges could be brought within 60 days, he said.

Here is what we have learned from the report.

New information about the investigation

- Authorities have determined how many victims were injured. Officials told reporters Friday that investigators determined 422 people suffered injuries as a direct result of gunfire, while another 851 individuals suffered other injuries during the attack. The report says all 22,000 people who attended the festival that night are recognized as victims.

- 31 victims were pronounced dead at the scene. The rest were pronounced dead at medical facilities they were taken to afterward. Police have previously said that 58 people died in the attack.

- Investigators have chased 1,965 leads in the case. They've also reviewed more than 21,000 hours of footage and issued 1,062 legal notices during the investigation.

Revelations about the gunman

- Investigators recovered "several hundred images of child pornography" on Paddock's hard drive. The investigation into the images in ongoing, the report says. CNN previously reported that Paddock's brother was charged with possession of child pornography.

- Paddock's doctor believed he may be bipolar. According to the report, Paddock's physician described him as "'odd" in behavior with "little emotion' shown." Though he believed Paddock could have had bipolar disorder, Paddock "did not want to discuss that topic further with him." Paddock refused anti-depressants but accepted prescriptions ordered for anxiety.

- He was described as "germaphobic." Paddockalso claimed multiple times to friends or family that he "felt ill, in pain or fatigued," the report said.

- Paddock paid off all his gambling debts before the shooting. It's already been reported that Paddock, a notorious gambler, was completely funded by his gambling habits and real estate transactions.

- Paddock's demeanor changed over the last year. His girlfriend, Marilou Danley, told investigators he had become "distant," the report says, "and their relationship was no longer intimate."

- The shooter's girlfriend believed buying guns was a hobby for Paddock. The 64-year-old purchased 55 firearms between October 2016 and September 2017, the report says. All of the guns recovered in the Mandalay Bay, with one exception, the report says, were purchased after September 2016.

Report sheds light on how he planned attack

- Paddock behaved strangely during a stay at the Mandalay Bay a month before the shooting. Paddock had specifically requested rooms that overlooked the Las Vegas Village. Danley, his girlfriend, told investigators that during their visit she "observed Paddock constantly looking out the windows of the room that overlooked the venue. Paddock would move from window to window looking at the site from different angles." Authorities said they don't anticipate charges being brought against Danley, who has cooperated with investigators.

- Google search history shows Paddock researched other large-scale venues. This isn't necessarily new -- it was previously reported he booked hotel rooms overlooking Lollapalooza in Chicago. But the report reflects inquiries dating back to May 18, 2017. At that time, Paddock was mostly looking into venues in Boston.

- Paddock googled "How tall is Mandalay Bay." Readers might remember that no suicide note or manifesto was found in Paddock's hotel room. The only piece of paper in the suite contained calculations the gunman made to determine how far his bullets would drop based on the height of his room, and the distance between himself and the venue. Paddock may have used the height of the hotel to calculate the trajectory.